The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the electronics industry utilized various methods and structures to build electrically programmable read only memory (EPROM) cells and devices. Typically each EPROM cell utilized an N-channel metal oxide semiconductor (NMOS) transistor that had a floating gate which was capacitively coupled to a control gate. Each cell also used a control transistor that applied an electrical potential to the control gate in order to program the EPROM. When the control transistor was energized in order to program the EPROM cell, a large depletion region was formed around the control gate. Because of this large depletion region, the control transistor typically was a large distance away from the control gate so that the depletion region would not adversely affect the programming operation. Examples such an EPROM cell along with the associated NMOS transistor and control gate are disclosed in U.S. Pat. No. 4,649,520 issued to Boaz Eitan on Mar. 10, 1987 and also in U.S. Pat. No. 5,747,846 issued to Makio Iida et al on May 5, 1998 both of which are hereby incorporated herein by reference.
One problem with previous EPROM cells was the area consumed by the EPROM cell. Because the control transistor was located a large distance away from the control gate, the EPROM cell occupied a large area.
Accordingly, it is desirable to have an EPROM cell that includes a floating gate and a control transistor, and that utilizes a small area.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.